Field
Embodiments of the disclosure generally relate to the field of semiconductor manufacturing processes and devices, more particularly, to methods of depositing silicon- or germanium-containing films for forming semiconductor devices.
Description of the Related Art
In general, selective epitaxy processes permit growth of epitaxial layers on a silicon surface with minimized epitaxial layer growth on a dielectric surface (e.g., oxides or nitrides). In order to maintain selectivity (i.e., to achieve preferential crystalline growth on silicon surfaces of the substrate with minimal growth on dielectric surfaces) during the epitaxy process, the deposition gases, halogen precursor, and reaction temperatures may be regulated and adjusted throughout the epitaxy process.
Current selective epitaxy processes have some drawbacks. To maintain selectivity during present epitaxial processes, chemical concentrations of the precursors and/or reaction temperatures must be regulated and adjusted throughout the deposition process. If not enough silicon precursor is administered, then the etching reaction may dominate, and the overall process is slowed down. Also, harmful over-etching of substrate features may occur. If not enough etchant precursor is administered, then the deposition reaction may dominate reducing the selectivity to form monocrystalline and polycrystalline materials across the substrate surface. Also, current selective epitaxy processes usually require a high reaction temperature, such as above 800° C. or higher. Such high temperatures are not desirable during some fabrication processes due to thermal budget considerations and possible uncontrolled nitridation reactions to the substrate surface. In addition, processing in the conventional manner with simultaneous deposition and etching at temperatures lower than about 800° C. results in unacceptably low growth rates in some cases.
Selective epitaxy processes may become even more challenging at lower growth temperatures, for example at or below about 600° C. At such temperatures, hydrogen chloride (HCl) dissociation efficiency becomes poor. As a result, amorphous silicon (aSi) or amorphous germanium (aGe) nucleation may occur on dielectric surfaces (e.g., SiO2 or SiN). Therefore, there is a need to have a process for selectively and epitaxially depositing silicon- or germanium-containing compounds while maintaining low process temperatures, such as about 600° C. or less.